FED-STD-228A
3.3.2 A section of the bath showing one aging container is shown on figure 4031. The container consists
of a nickel-plated brass cylinder 4 ½ inches in diameter and 8 3/8 inches high with a cover which rests on
a flange inside the cylinder about 2 inches from the top. The space above the cover is filled with thermal
insulating material. Circulation of air is by convection through a ¼-inch inside diameter tube mounted in
the metal cover. One of the tubes extends to within about ½ inch of the bottom of the container and the
other one extends about 6 inches above the cover. The latter tube is insulated with cork.
3.3.3 A water or other liquid bath capable of holding several submerged specimen containers and
equipped with an automatic thermostatic control and means for obtaining a uniform temperature in all
parts of the bath. The temperature of the air at the specimen will be approximately 0.5°C (1°F) below that
of the liquid bath. The bath is equipped with a cover containing about 1 inch of thermal insulating
material. Several aging containers are fitted into the bath with the top being flush with the cover of the
bath.
3.3.4 Means for suspending the specimens vertically in the aging container without touching each other
or the sides of the container. This can be accomplished by fastening hooks to the underside of the cover.
4. PROCEDURE
4.1 Unless otherwise specified in the detail specification, the test shall be carried out at a temperature of
70° ± 1°C (158° ± 2°F) for a period of 166 hours ± 1 hour.
4.2 Unless otherwise specified in the detail specification, tensile strength and elongation tests, methods
3021 and 3031 respectively, shall be used to determine the deterioration of the insulation or sheath due
to aging.
4.3 After adjusting the aging container to the required temperature, the specimen shall be suspended
vertically and the container closed immediately. At least 10 milliliters of capacity shall be available in the
container for each gram of oxidizable material. The exposure period shall start at the time the specimen
is placed in the aging container and shall continue for the required time under the required conditions
without opening the container.
4.4 At the end of the exposure period, the specimen shall be removed from the aging container and set
aside on a flat surface to rest for not less than 16 hours and not more than 96 hours at room temperature,
before tests are conducted.
4.5 At the end of the rest period, unless otherwise specified in the detail specification, tensile strength
and elongation shall be determined on the aged specimen as described in methods 3021 and 3031. If
other properties are required the specimen shall be tested as described in the specified method. The
same test shall be conducted on aged and unaged specimens for the purpose of comparison in
determining the degree of deterioration of the aged material.
5. RESULTS
5.1 Calculation. The change in tensile strength, elongation or other characteristic of the insulation or
sheath of the inspection unit due to aging shall be calculated as follows:
Change in characteristic, percent=O-E x 100
O
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